Pulverizer with basket-type rotor



Dec. 6, 1966 H. A. MERGES ETAL 3,289,952

PULVERIZER WITH BASKET-TYPE ROTOR 2 Sheets-Sheet 1 Filed April 21, 1964 Fig. I

10 venfor.

Dec. 6, 1966 H. A. MERGES ETAL 3,289,952

PULVERIZER WITH BASKET-TYPE ROTOR Filed April 21, 1964 2 Sheets-Sheet Z United States Patent 3,289,952 PULVERIZER WITH BASKET-TYPE ROTQR Herbert Alfred Merges, 2 Werkstrasse, Wolfgang, Germany, Hans Georg Krestin, 3 Feltlstrasse, Ostheim, Germany, and Egon Becker, Frankfurter Ldstla, Hanan, Germany Filed Apr. 21, 1964, Ser. No. 361,359 Claims priority, application Germany, Apr. 26, 1963, C 29,772 4 Claims. (Cl. 24149) This invention relates to a pulverizing mill with baskettype rotor carrying grinding elements and also serving to produce an air current in the grinding chamber of the mill.

Such a rotor comprises an annular disk extending from the hub, a supporting ring spaced from the disk and a plurality of axially extending, parallel spacing rods connecting the disk and the ring along the periphery of the rotor. The rotor disk and the annular ring carry grinding elements, such as plate or blade members. Clamping rings are attached to the annular ring and the rotor disk, which rings overlap lugs at opposite ends of the grinding elements thereby securing them to the rotor.

Pulverizers with rotors of the type described above have the disadvantage that they are exposed to elevated temperatures at the front and back walls of the mill housing adjacent the holding rings of the rotor. This is particularly true where tough, elastic materials, such as polyethylene, polypropylene, polyamide, rigid polyvinyl chloride, and plasticized PVC, are to be pulverized. These elevated temperatures are due to the fact that part of the feed escapes the action of the grinding elements and is laterally displaced beyond the end faces of the rotor and is sucked into the interior of the rotor. Thus part of the feed is circulated through the rotor of the mill whereby the front cover of the mill housing is heated.

Furthermore, the rear of the housing is heated also, particularly, if the rotor disk has apertures, as is the case with conventional rotor disks. The lateral escape of part of the feed is particularly pronounced where the outlet screen through which the material is fed is wider than the grinding elements. Thus where tough, elastic materials are pulverized by the combined effect of the wide screen and the narrower pulverizing elements, feed particles may escape into the annular spaces between the rotor clamping rings and the cover or back-plate of the mill housing where they are rotated with the rotor without being pulverized because of the air leaving the rotor and the screen laterally. This is accompanied by heavy friction and generation of heat, which cause the feed to be plasticized or intered.

In cases in which such pulverizers are used to grind crystalline feeds, such as sugar and salt, a finely ground product is obtained because of the high efiiciency of the pulverizing elements, the size of the ground particles being much smaller than that of the perforations in the screen through which the material is fed. Hence, if the width of the pulverized elements is smaller than the width of the screen, part of the not yet finely ground feed can escape the range of action of the elements and passes through the screen at the outer portions without being ground so that it is coarser than the fines passing through the screen near the grinding elements.

It is accordingly a primary object of the invention to provide a pulverizer in which the possibility of overheating is minimized.

Still another object of the invention is to provide a mill with means effectively preventing feed particles from passing laterally by the grinding rotor without being ground.

According to the invention, the end faces of the rotor clamping rings have spaced bosses defining radial recesses in the end faces of the rings. By this arrangement an ad- 3,289,952 Patented Dec. 6, 1966 ditional air stream is produced, which has the following advantages:

First, an effective flow of gas, such as air, is produced in the annular spaces between the rotor and the front or back wall of the housing, thereby preventing the feed from lodging in these spaces.

Secondly, this air stream has a cooling effect on the front and back walls of the mill housing because it flows over and along the inner surfaces of those walls.

Thirdly, the air stream passing through the mill and carrying ground particles is prevented from being displaced in the grinding chamber laterally in the direction of the front and back walls of the housing. Hence, no coarser particles, that is, particles, not yet ground to the desired degree of fineness, are permitted to enter these regions, whence they would pass through the screen and appear as undesired oversize in the finished product.

For grinding certain materials, such as insecticides or bactericides, it has been proven necessary to itensify the advantageous effects described before. For this purpose, vane members are provided according to the invention. These vane members are arranged on the supporting ring and/ or on the rotor disk. They can be disposed radially, secantially, or tangentially with respect to the aperture in the supporting ring.

Further objects and advantages of the invention will become apparent from the following detailed description, when read in conjunction with the drawings, in which FIGURE 1 is a cross-sectional view of a mill with the rotor of the invention;

FIGURE 2 is an end elevation of the rotor of the invention, and

FIG. 3 is a perspective view of the rotor of the invention.

Referring now more particularly to the figures, there is shown a supporting ring 1 arranged at the inlet side of the mill. Ring 1 has slots 4 in which the lugs 3 of grinding elements constituted by blade members 2 are inserted. Blade members 2 are held in place by clamping ring 5 and like clamping ring 5' overlapping the lugs at the opposite ends of blade members 2. The rotor includes a disk 9 secured to drive shaft 10. Axially parallel spacing rods 11 hold the front suporting ring 1 at a predetermined distance from the annular rim of rotor disk 9. The entire rotor structure is surrounded by a screen basket 13 disposed in the mill housing 12.

Clamping rings 5 and 5' have spaced bosses 6 on their faces to define recesses 7 therebetween. Vane members 8 and 8' are disposed on the face end of supporting ring 1, with members 8 slightly extending beyond the inner edge of supporting ring 1, in the direction of the rotor axis.

Vane members 8 and 8' serve to aid in the air flow in the space between the rotor and the mill housing. These vane members are used particularly if the mill is employed to grind insecticides, 'bactericides, fungicides, or the like. To control the air flow produced by the additionally provided vane members 8" over a certain range, secondary air inlets 14 extending through the back wall of the housing are provided which can be closed.

In the foregoing, a specific embodiment of the invention has been described, but is should be understood that modifications and changes may be made Without departing from the spirit and scope thereof.

What is claimed is:

1. A mill comprising (1) a housing having a back wall and a front wall, the

walls defining a grinding chamber therebetween;

(2) a rotor mounted in said grinding chamber and rotatable about an axis extending between said walls, the rotor including (a) a disk having an annular rim,

(b) a supporting ring spaced from the disk rim and coaxial therewith, the disk rim and ring constituting end faces of the rotor, and

(c) a plurality of axially extending, parallel spacing rods connecting the disk and the ring along the periphery of the rotor;

(3)' a plurality of grinding elements supported on the disk rim and supporting ring over the periphery of the rotor; and

(4) clamping rings mounted over the disk rim and supporting ring to hold the grinding elements in place, annular spaces being defined between end faces of the clamping rings and the walls of the housing,

(d) spaced bosses being arranged on the end face of at least one of the clamping rings defining therebetween radially extending recesses.

2. The mill of claim 1, further comprising vanes mounted on at least one of the end faces of the rotor.

3. The mill of claim 2, further comprising a primary 4 means in the other one of the housing walls, and said vanes being mounted on the rotor end face associated with the other wall.

4. The mill of claim 1, further com-prising a baskettype screen surrounding the rotor and extending between the mill housing walls.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 6/1939 Great Britain. 4/1953 Great Britain.

ROBERT c. RIORDON, Primary Examiner.

air inlet in one of the housing walls, secondary air inlet 20 D. G. KELLY, Assistant Examiner. 

1. A MILL COMPRISING (1) A HOUSING HAVING A BACK WALL AND A FRONT WALL, THE WALLS DEFINING A GRINDING CHAMBER THEREBETWEEN; (2) A ROTOR MOUNTED IN SAID GRINDING CHAMBER AND ROTATABLE ABOUT AN AXIS EXTENDING BETWEEN SAID WALLS, THE ROTOR INCLUDING (A) A DISK HAVING AN ANNULAR RIM, (B) A SUPPORTING RING SPACED FROM THE DISK RIM AND COAXIAL THEREWITH, THE DISK RIM AND RING CONSTITUTING END FACING OF THE ROTOR, AND (C) A PLURALITY OF AXIALLY EXTENDING, PARALLEL SPACING RODS CONNECTING THE DISK AND THE RING ALONG THE PERIPHERY OF THE ROTOR; 